Mobile ip addressing

ABSTRACT

A system and method are provided for mobile Internet Protocol (IP) addressing, in a multi-mode wireless communications access terminal (AT). The method provides an AT with an IP address (ATA), and a care-of-address (CoA) in each of a plurality of networks. In one aspect, the AT selects a first network for transmission, from the plurality of networks. The AT sends an IP packet to a correspondent node (CN) via a first mobile node (MN) external device. Regardless of the network selected, the AT is able to use the ATA as a source address. Sending the IP packet to the CN may include creating a tunnel between the first MN and the HA. The IP packet is sent to the HA using the first CoA as a tunnel source address, and the HA sends the IP packet to the CN using the ATA as the source address.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 11/347,506, filed Feb. 2, 2006 and titled MOBILE IP ADDRESSING,which is hereby expressly incorporated by reference.

BACKGROUND

1. Field

The present invention generally relates to wireless communications and,more particularly, to a mobile Internet Protocol (IP) system and methodfor addressing a wireless transponder access terminal (AT).

2. Background

Traffic on the Internet is growing exponentially due to an increasingnumber of subscribers and the introduction of new applications. Widearea wireless networks are also experiencing rapid subscriber growth.Currently, there are many efforts underway to provide data services onwireless access networks.

To facilitate data services in mobile wireless telecommunicationsystems, it is desirable to allow mobile wireless nodes to change theirlink-layer point of network attachment without reassigning a new networkaddress. According to current data network telecommunication standardsfor mobile equipment in general (e.g., the “Mobile IP” standardspromulgated by the Internet Engineering Task Force (IETF) or the GeneralPacket Radio Service (GPRS) standards proposed by the EuropeanTelecommunication Standards Institute (ETSI)), one way to provide thedesired network address transparency is to employ “mobility agents.”These are network routing nodes that route communication content onbehalf of mobile nodes as they move around the network. For example,according to the IETF Mobile IP standards, a mobile node's mobilityagents may consist of a “home agent” routing node and may also include a“foreign agent” routing node. The home agent is a routing node in themobile node's sub-network that maintains a network interface on the linkindicated by the mobile node's “home address,” which is a networkaddress intended to remain assigned to the mobile node for an extendedtime period. When the mobile node is away from its home sub-network, thehome agent intercepts communication content bound for the mobile node'shome address and tunnels it for delivery to a “care-of-address” assignedto the mobile node, when the mobile node registers on a foreignsub-network. The care-of address may be the address of a foreign agentrouting node in the foreign sub-network.

Correspondent nodes wishing to communicate with a foreign-registeredmobile node are able to address their communication content to themobile node's home address. Transparently, the communication content istunneled to the mobile node's care-of-address and delivered to themobile node on the foreign sub-network. Normal routing may be used forsending return communication content from the mobile node to thecorrespondent node.

The above-mentioned routing mechanism can be used for mobile wirelessnodes connected to a foreign sub-network via an air interface. However,a problem may arise if the mobile wireless node is being activelytransported while communicating over the data network, and a callhandoff is required from one radio base station to another. In thatcase, the old base station may be linked to one care-of-address, whilethe new base station is linked to another care-of-address. Call handoffthen requires that the communication tunneling endpoint be transferredfrom the old care-of-address to the new care-of-address.

Further, in some cellular telephony architectures a care-of-addressendpoint located in the core network is utilized as the addressedcommunication, e.g. target Internet Protocol Address, for datacommunication with a wireless communication apparatus or terminal. Insome instances, the endpoint may be a packet data service node (PDSN), abase station controller (BSC), or the like. A handoff between PDSNendpoints may be required to maintain a minimum level of communicationswith the mobile wireless node, for instance due to conditions in thecore network such as congestion or latency to the mobile wireless node.A PDSN handoff then requires that the communication tunneling endpointbe transferred from the care-of-address of the old PDSN, to thecare-of-address of the new PDSN.

Transferring the tunneling endpoint of the care-of-address may creategaps that interrupt the timely delivery of call content, or result inout-of-order delivery of content, both of which can degradecommunication quality, particularly for voice telephony. Such gaps arisefrom the inability of the data network to coordinate well with the airinterface so as to determine the exact time of handoff. Delays can occurbetween the point of handoff and the point at which the home agentbegins routing communication content to the new care-of-address.

It would be advantageous if a telecommunication system serving mobilewireless access terminals could provide improved call handoff withoutloss of communication content. It would also be advantageous if thetunneling endpoint care-of address could be maintaining withouttransfers or handoffs.

SUMMARY

Multi-mode wireless communications access terminals (ATs), devicescapable of communicating in different types of networks, are becomingmore common. For example, an AT may be capable of communicating in bothan IEEE 802.11 network and a CDMA cellular network. Conventionally, suchan AT has a different IP address for each network. Network handoffs arecomplicated by the fact that the networks have different geographiccoverage areas and quality of service (QoS) capabilities. Further,although different networks may all be connected to the Internet,communications between networks is still an evolving issue.

The instant invention uses a home agent (HA) to manage sessioncontinuity for multi-mode AT communications, where each mode isassociated with a different network. The HA cross-references an AT'smobile IP (MIP) address with a care-of-address (CoA) in each network.Thus, the HA is able to direct IP packets via a particular network on apacket-by-packet basis, or send duplicate packets via multiple networksfor improved reliability.

Accordingly, a method is provided for mobile IP addressing, in amulti-mode wireless communications AT. The method provides an AT with anIP address (ATA), and a CoA in each of a plurality of networks. In oneaspect, the AT selects a first network for transmission, from theplurality of networks. The AT sends an IP packet to a correspondent node(CN) via a first mobile node (MN) external device, and regardless of thenetwork selected, the AT is able to use the ATA as the source address inthe packet header.

Sending the IP packet to the CN may include creating a tunnel betweenthe MN and the HA. The IP packet is sent to the HA using the first CoAas a tunnel source address, and the HA removes the tunnel headerinformation and sends the IP packet to the CN with the ATA as the sourceaddress.

In another aspect, the AT receives an IP packet from the CN with the ATAlisted as a destination address, via a MN external device. Again, theATA can be used as the destination address in the IP packet header,regardless of the network selected. More particularly, receiving an IPpacket from the CN may include the CN sending the IP packet to the HA,and the creation of a tunnel between the HA and the MN. For example, theIP packet can be sent to the first MN with a first CoA listed as atunnel destination address, and the first MN can remove the tunnelheader information and send the IP packet to the AT, with the ATA listedas the destination address.

Additional details of the above-described method, and a multi-modewireless AT system for sending IP packets through the use of MIPaddressing are described below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram of a multi-mode wirelesscommunications access terminal (AT) system for sending Internet Protocol(IP) packets using mobile IP (MIP) addressing.

FIG. 2 is a schematic block diagram featuring a first variation of theAT MIP addressing system of FIG. 1.

FIG. 3 is a schematic block diagram featuring a second variation of theAT MIP addressing system of FIG. 1.

FIG. 4 is a diagram depicting the digital wrapper used for transportingan IP packet from the AT to the CN.

FIG. 5 is a schematic block diagram of a multi-mode wirelesscommunications AT system for receiving IP packets using MIP addressing.

FIG. 6 is a diagram depicting the digital wrapper used for transportingan IP packet from the CN to the AT.

FIG. 7 is a diagram depicting TCP/IP protocol stack, as modified for usewith the present invention MIP addressing system.

FIG. 8 is a diagram depicting a variation of the MIP addressing protocolstack of FIG. 7.

FIG. 9 is a flowchart illustrating a method for MIP addressing in amulti-mode wireless communications access AT.

FIG. 10 is a flowchart illustrating a variation in the method for MIPaddressing in a multi-mode wireless communications AT.

FIG. 11 is a schematic block diagram featuring a third variation of themulti-mode wireless communications AT of FIG. 1.

DETAILED DESCRIPTION

FIG. 1 is a schematic block diagram of a multi-mode wirelesscommunications access terminal (AT) system for sending Internet Protocol(IP) packets using mobile IP (MIP) addressing. The system 100 comprisesan AT 102. The access terminal may be referred to by those skilled inthe art as a handset, a wireless communications device, user terminal,user equipment, mobile station, mobile unit, subscriber station,subscriber unit, mobile radio, radio telephone, wireless station,wireless device, or some other terminology. The various conceptsdescribed throughout this disclosure are intended to apply all wirelesscommunication devices regardless of their specific nomenclature. Sincethe AT is multi-mode, it includes a plurality of communicationsubsystems having wireless transceivers for communicating with externaldevice mobile units (MNs) in a corresponding plurality of networks. Afirst subsystem 104, for communicating with a first network 106, and asecond subsystem 108, for communicating with a second network 110, areshown. However, it should be understood that the AT 102 is not limitedto any particular number of subsystems. For example, the subsystems maybe capable of communicating with Ethernet, Bluetooth, IEEE 802.11, IEEE802.15, Code Division Multiple Access (CDMA) telephone, or Global Systemfor Mobile communications (GSM) telephone networks, to name a fewpossible examples. The AT 102 is not limited to any particular type ofwireless communications, and in some aspects, wired communications aresupported.

A MIP addressing module 112 has communication subsystem interfaces 114and 116, connected to subsystems 104 and 108, respectively. The MIPaddressing module 112 has an AT IP address (ATA) that iscross-referenced to a care-of-address (CoA) for each of the plurality ofMNs. As shown, the MIP addressing module 112 selects the first network106 for transmission, and sends an IP packet to a correspondent node(CN) 118. As explained below, the MIP addressing module send the IPpacket via a first MN 120, using the ATA as the source address.

Alternately, the MIP addressing module 112 may be understood to be aprocessing device, which can be enabled with a microprocessor 150 andmicroprocessor executable instructions stored in memory 152. In someaspects, some or all of the processor steps can be enabled using a statemachine or electronic circuitry. In this case, the processing device 112comprises interfaces 114 and 116 for a plurality of communicationsubsystems 104/108 wirelessly communicating with external device MNs120/122 in a corresponding plurality of networks 106/110. The memory 152stores the AT ATA. A network address selector 154 sends IP packets to CN118 using the ATA as the source address, via the first MN 120 with thefirst CoA (FIG. 1), the second MN 122 with the second CoA (FIG. 2), or acombination of the two MNs (FIG. 3).

FIG. 2 is a schematic block diagram featuring a first variation of theAT MIP addressing system of FIG. 1. As shown, the AT MIP addressingmodule 112 selects the second subsystem for transmission 108, and sendsan IP packet to the CN 118. The packet is sent via a second MN 122 inthe second network 110, via interface 124, using the ATA as the sourceaddress.

FIG. 3 is a schematic block diagram featuring a second variation of theAT MIP addressing system of FIG. 1. Here, the AT MIP addressing module112 selects the second subsystem 108 for transmission, in addition tothe first subsystem 104. The MIP addressing module 112 sends IP packetsto the CN 118 using the ATA as the destination address. The packets aresent via the first MN 120 associated with the first network 106, and viathe second MN 122 associated with a second network 110. FIG. 4 is adiagram depicting the digital wrapper used for transporting an IP packetfrom the AT 102 to the CN 118. Viewing both FIGS. 1 and 4, the first MN120 has a first network interface 130 (represented as an antenna) forreceiving the IP packet from the AT 102 with the ATA listed as thesource address. The first MN 120 has a tunnel interface 132 for sendingthe IP packet, using a first CoA as the tunnel source address. A homeagent (HA) 134 has a tunnel interface 136 for receiving the IP packetfrom the first MN 120. The HA 134 has a network interface 138 to sendingthe IP packet to the CN 118, with the ATA listed as the source address.It should be understood that although the interface 130 and the first MN120 are shown as a common device, they need not necessarily beco-located. In other aspects not shown, data can be communicated fromthe air interface 130 to the first MN 120 through a communication link.Further, the interface 136 from the first MN and the interface 124 fromthe second MN 122 (see FIG. 2) may be the same interface. Likewise, theHA to CN interface 138 may also be the same, regardless of whether thefirst or second network is used.

As shown, the HA 134 includes a memory 140 where the AT's ATA iscross-referenced to each CoA. CoA1 is shown associated with the first MN120 in the first network 106. CoA2 is shown associated with the secondMN 122 in the second network 110. The CoAs may be registered in the HA134 by the AT 102, the MN (either first MN 102 or second MN 122), or acombination of the AT 102 and the MN(s).

FIG. 5 is a schematic block diagram of a multi-mode wirelesscommunications AT system for receiving IP packets using MIP addressing.The system 500 comprises AT 102, with the first communication subsystem104 and the second communication subsystem 108, as shown in FIG. 1.Again, the MIP addressing module 112 has communication subsysteminterfaces and an AT ATA cross-referenced to CoAs for the first MNexternal device 120 and the second MN external device 122. The MIPaddressing module 112 receives an IP packet from the CN 118, via thefirst MN 120. The IP packet lists the ATA as the destination address,via the first MN 120.

As explained in the description of FIG. 1, the MIP addressing module 112may be understood as a microprocessor 150, memory 152, and MIPaddressing section 154. As explained above, the MIP addressing module112 comprises interfaces 114 and 116 for a plurality of communicationsubsystems 104/108 wirelessly communicating with external device MNs120/122 in a corresponding plurality of networks 106/110. The memory 152stores the AT ATA. In this aspect, the network address selector 154receives IP packets from CN 118 with the ATA listed as the destinationaddress, via the first MN 120, the second MN 122, or both MNs.

FIG. 11 is a schematic block diagram featuring a third variation of themulti-mode wireless communications AT of FIG. 1. The AT 1100 includesmeans for wirelessly communicating with external device mobile units(MNs) in a plurality of networks. Two wireless communication means 1102and 1104 are shown, however, the AT is not limited to any particularnumber. Also shown is a means for network selection 1106. The networkselection means 1106 has an AT IP address (ATA) cross-referenced to acare-of-address (CoA) for each of the plurality of MNs. MNs 120 and 122are shown. The network selection means 1106 selects a first network fortransmission (i.e., network 106), and sends an IP packet to CN 118 usingthe ATA as the source address, via the first MN 120. In another aspect,the network selection means 1106 receives an IP packet from the CN 118with the ATA listed as the destination address, via the first MN 120.

FIG. 6 is a diagram depicting the digital wrapper used for transportingan IP packet from the CN 118 to the AT 102. Viewing both FIGS. 5 and 6,the HA 134 has a network interface 138 for receiving the IP packet fromthe CN 118, with the ATA listed as the destination address. The HA 134has a tunnel interface 136 for sending the IP packet with the first CoAlisted as the tunnel destination address. The first MN 120 has a tunnelinterface 132 for receiving the IP packet, and a network interface 130for sending the IP packet to the AT 102. The first MN 120 sends the IPpacket to the AT 102 with the ATA listed as the destination address.

The network that is used for sending the IP packet to the AT 102 may beconfigured by a number of different elements, including the AT 102, theHA 134, the first MN 120 (or second MN 122), or a combination of the AT,HA and MN(s). If the HA 134 makes the selection, a packet filter 142 maybe configured to use selection criteria such as the source address,destination address, source port, destination port, type of service,protocol type, packet size, traffic class, or flow label. Othercriteria, well known by those skilled in the art, could also be used inthe design of the packet filter 142.

Although not specifically shown in FIGS. 5 and 6, in other aspects ofthe system, IP packets can be sent from the CN 118, to the AT 102, usingthe second network 110, or both the first and second networks. It shouldalso be understood that although only two networks, and twocorresponding AT communication subsystems are shown, the system 500 isnot limited to any particular number of networks or AT communicationsubsystems.

Functional Description

In IP networks, routing is based on stationary IP addresses, just as apostal letter is delivered to the fixed address on the envelope. Adevice on a network is reachable through normal IP routing, using anetwork-assigned IP address. This fixed-address scheme begins to breakdown when a device roams away from its home network and is no longerreachable using normal IP routing, which may result in an active sessionbeing terminated. Mobile IP was created to enable users to keep the sameIP address, while traveling to a different network carrier, or using adifferent technology, to ensure that sessions or connections are notdropped.

Because the mobility functions of Mobile IP have been conventionallyperformed at the network layer, rather than at the physical layer, theAT can span different types of wireless and wireline networks whilemaintaining connections and ongoing applications. Remote login, remoteprinting, and file transfers are some examples of applications where itis undesirable to interrupt communications while an individual roamsacross network boundaries. Also, certain network services, such assoftware licenses and access privileges, are based on IP addresses.Changing these IP addresses can compromise the network services.

FIG. 7 is a diagram depicting TCP/IP protocol stack, as modified for usewith the present invention MIP addressing system. Conventionally, mobilestations (i.e., WLAN devices) have been dependent upon Physical Media.For example, an IEEE 802.11b device must undergo a re-associationprocedure when it acquires a new access point (AP). As mentioned above,the Internet assumes the use of static device locations and addresses.As a result, when a conventional mobile device reconnects in a newlocation, a new IP address must be obtained. Further, a new defaultrouter address and DNS server address must be obtained. If the mobilestation is a computer, a change in IP address usually requires that thenetwork interface for the device be restarted. Typically, any previouslyrunning applications using the network interface are likely to stopworking properly.

Conventional IP addresses are used for two purposes: host identificationand routing. With respect to the identification of a host, the TCP/IPstack typically identifies the source IP address as the endpoint. Theseaddresses correspond to specific locations on the Internet. MIP is asolution that is independent of the Physical and data layers. MIPaddressing creates a location-independent identifier for an AT, whilecreating a new type of location-dependent address. A permanent IPaddress, also referred to herein as a home address or ATA is used toidentify the AT. Another address, which may change depending upon thelocation of the AT, referred to herein as the CoA, is used for routing.

As described in the explanation of FIGS. 1 through 6, a mobile node (MN)can be thought of as a device that maintains an immediate link with theAT, even if the AT is roaming. However, it should be understood that aroaming AT may acquire different MNs as it roams through a network.Acquiring a new MN may require that the AT obtain a new CoA. The ATcommunicates with a MN in each network, and the CoA can be thought of asthe intermediary address between the HA and AT. Unlike conventional MIP,the MN of the present invention system is also located in a deviceexternal to the AT. In one aspect, there is a separate MN for eachnetwork interface used by the AT.

The Home Agent is a router, typically located in the AT's home network,which serves as the anchor point for communication with the MN. The HAtunnels packets from a CN device on the Internet, to the MN.Conventionally, a foreign agent is a router that may function as thepoint of attachment for the Mobile Node when it roams to a foreignnetwork, delivering packets from the Home Agent to the Mobile Node.However, since the MN of the present invention system is external to theAT, and therefore, not necessarily roaming, the functions previouslyassociated with the foreign agent are performed by the MN in the presentinvention.

The care-of-address is the termination point of the tunnel in the MobileNode. The Home Agent maintains an association between the AT's ATA andits care-of address, which is the address of the Mobile Nodecommunicating with the AT. The AT is able to send and receive packetsusing its home IP address, effectively maintaining the appearance thatit is always on its home network. Even when the AT is roaming in foreignnetworks, its movements are transparent to correspondent nodes.

The systems described in FIGS. 1 through 6 may be arranged to support anarrangement of networks, where the AT is able to communicate indifferent networks having complementary strengths. For example, the ATmay be registered with an HA for a number of networks, to receive datasimultaneously over multiple radio access technologies (RAT), for thepurpose of redundancy. Alternately, the AT may use one network (i.e., acellular network) for paging, and a different network (i.e., a wirelessLAN) for packet forwarding. In one aspect, the HA manages the use ofnetworks using a predetermined policy. In a different aspect, the ATuses messaging to manage network use, and to configure the HA and MNdevices. Further, the HA may also be configured to dynamically updatehow and where packets are sent, based on data traffic received from theAT. For example, paging through a first network may occur as a result ofdata packets being received at the HA.

The AT may be configured for listening to only a first network forpaging. When a page is received, the AT may access the network on whichit was paged, access another network, or access multiple networkssimultaneously (for redundancy). The HA may be configured differently,based on AT capabilities and policy, to support each mode of access.

With respect to handoffs, the HA may be configured to forward a packetto multiple RAT networks. A multi-mode AT may simultaneously downloadfrom two RAT networks during handoff. The AT may switch to a destinationnetwork, once the same packet is received from both networks, or it mayswitch when it receives a message from the HA in the data stream.

FIG. 8 is a diagram depicting a variation of the MIP addressing protocolstack of FIG. 7. In this figure, a mobile node (MN) is located at theAP. A MIP tunnel is created between the HA and the AP (MN) in the firstnetwork. Although not specifically shown, the second network has anequivalent protocol stack, with the AT using the second network MAC/PHYaccess layers.

With respect to registration, different filter sets can be defined foran AT, with a destination CoA associated with each filter. That is, adifferent packet forwarding policy can be configured for each filter.With respect to forwarding, MIP can be used to manage the forwarding ofpacket flows during a connection. In another aspect, a packet flow'sbehavior may be dynamically updated based on data traffic received fromthe AT.

FIG. 9 is a flowchart illustrating a method for MIP addressing in amulti-mode wireless communications access AT. In combination with FIG.5, the flowchart may represent a signal bearing medium tangiblyembodying a program of machine-readable instructions executable by adigital processing apparatus to perform operations for MIP addressing ina multi-mode wireless communications AT. Although the method is depictedas a sequence of numbered steps for clarity, the numbering does notnecessarily dictate the order of the steps. It should be understood thatsome of these steps may be skipped, performed in parallel, or performedwithout the requirement of maintaining a strict order of sequence. Themethod starts at Step 900.

Step 902 provides an AT having an IP address (ATA) and a CoA in each ofa plurality of networks, see the explanation of FIG. 1 above. Step 904selects a first network for transmission from the plurality of networks.Step 906 sends an IP packet to a CN via a first MN external device,using the ATA as a source address.

Alternately, Step 905 selects a second network for transmission, andStep 908 sends an IP packet to the CN via a second MN external deviceusing the ATA as the source address. In another aspect, Steps 904 and905 are both preformed. That is, the second network is selected fortransmission, in addition to the first network. Then, Step 906 and 908are both performed.

In a different aspect, Step 902 includes creating a tunnel between thefirst MN and the HA, and sending the IP packet to the CN in Step 906 (orStep 908) includes substeps. Step 906 a sends the IP packet to the HAusing the first CoA as a tunnel source address. Step 906 b sends the IPpacket from the HA to the CN using the ATA as the source address.

In one aspect Step 903 registers the CoAs with the HA, from a sourcesuch as the AT, the MN(s), or a combination of the AT and the MN(s).

FIG. 10 is a flowchart illustrating a variation in the method for MIPaddressing in a multi-mode wireless communications AT. The method startsat Step 1000. Step 1002 provides an AT having an IP address (ATA) and aCoA in each of a plurality of networks. Step 1004 selects a firstnetwork from the plurality of networks. Step 1006 receives an IP packetfrom a CN with the ATA listed as a destination address, via a first MNexternal device.

In one aspect, Step 1002 creates a tunnel between the HA and the firstMN, and receiving an IP packet from the CN in Step 1006 includessubsteps. Step 1006 a sends the IP packet from the CN to the HA. Step1006 b sends the IP packet to the first MN with a first CoA listed as atunnel destination address. Step 1006 c sends the IP packet from thefirst MN to the AT, with the ATA listed as the destination address.

In one aspect, selecting the first network in Step 1004 includesselecting the first network from a source such as the AT, the HA, theMN, and a combination of the AT, HA and MN. If the HA selects the firstnetwork, it may use packet filter criteria such as source address,destination address, source port, destination port, type of service,protocol type, packet size, traffic class, or flow label, to name a fewexamples.

In a different aspect, Step 1004 selects the first network and a secondnetwork. A further step, Step 1005, receives a paging message via asecond MN associated with a second network, prior to receiving the IPpacket. Then, receiving the IP packet in Step 1006 includes accessingthe first network in response to receiving the paging message, andreceiving the IP packet via the first network.

In one aspect, Step 1004 selects the first network and the secondnetwork, and receiving the IP packet from the CN in Step 1006 includesreceiving IP packets via a second MN associated with the second network,in addition to receiving IP packets via the first MN associated with thefirst network. In a different aspect Step 1008 sends an IP packet to anHA via the first network. Then, in Step 1010 the HA ceases to forward IPpackets on a second network, in response to the AT sending the IP packetvia the first network in Step 1008. Alternately, the AT may send aredirect message to the HA in Step 1008, and in Step 1010 the HA ceasesto forward IP packets on a second network in response to sending theredirect message. That is, packets are received only via the selectedfirst network.

In another aspect, Step 1008 sends an IP packet to an HA via the secondMN associated with a second network. Step 1009 selects the secondnetwork in response to the AT sending the IP packet, and Step 1010subsequently receives IP packets via the second MN.

A system and method have been described for using MIP addressing in awireless communications AT. Some examples of specific protocols, networktypes, and signaling have been provided to illustrate the invention.However, the invention is not limited to merely these examples. Othervariations and embodiment of the invention will occur to those skilledin the art.

1. In a multi-mode wireless communications access terminal (AT), amethod for mobile Internet Protocol (IP) addressing, the methodcomprising: providing an AT having an IP address (ATA) and acare-of-address (CoA) in each of a plurality of networks; from theplurality of networks, selecting a first network for transmission; and,sending an IP packet to a correspondent node (CN) via a first mobilenode (MN) external device, using the ATA as a source address.
 2. Themethod of claim 1 further comprising: selecting a second network fortransmission; and, sending an IP packet to the CN via a second MNexternal device using the ATA as the source address.
 3. The method ofclaim 1 further comprising: selecting the second network fortransmission, in addition to the first network; and, sending IP packetsto the CN via the first MN with a first CoA, and via a second MN with asecond CoA, using the ATA as the source address.
 4. The method of claim1 wherein providing the AT having the ATA and the CoA in each of aplurality of networks includes creating a tunnel between the first MNand the HA; wherein sending the IP packet to the CN includes: sendingthe IP packet to the HA using the first CoA as a tunnel source address;and sending the IP packet from the HA to the CN using the ATA as thesource address.
 5. The method of claim 4 further comprising: registeringthe CoAs with the HA, from a source selected from the group consistingof the AT, the MN, and a combination of the AT and the MN.
 6. Amulti-mode wireless communications access terminal (AT) system forsending Internet Protocol (IP) packets using mobile IP (MIP) addressing,the system comprising: an AT comprising: a plurality of communicationsubsystems having wireless transceivers for communicating with externaldevice mobile units (MNs) in a corresponding plurality of networks; and,a MIP addressing module having communication subsystem interfaces and anAT IP address (ATA) cross-referenced to a care-of-address (CoA) for eachof the plurality of MNs, the MIP addressing module selecting a firstnetwork for transmission, and sending an IP packet to a correspondentnode (CN) using the ATA as the source address, via a first MN.
 7. Thesystem of claim 6 wherein the AT MIP addressing module selects a secondsubsystem for transmission, and sends an IP packet to the CN using theATA as the source address, via a second MN.
 8. The system of claim 6wherein the AT MIP addressing module selects the second subsystem fortransmission, in addition to the first subsystem, and sends IP packetsto the CN using the ATA as the destination address, via the first MNassociated with the first network, and via a second MN associated with asecond network.
 9. The system of claim 6 further comprising: a first MNhaving a first network interface for receiving the IP packet from the ATwith the ATA listed as the source address, the first MN having a tunnelinterface for sending the IP packet, using a first CoA as the tunnelsource address; and a home agent (HA) having a tunnel interface forreceiving the IP packet from the first MN, and a network interface tosending the IP packet to the CN with the ATA listed as the sourceaddress.
 10. The system of claim 9 wherein the CoAs are registered withthe HA, from a source selected from the group consisting of the AT, theMN, and a combination of the AT and the MN.
 11. A multi-mode wirelesscommunications access terminal (AT) processing device for sendingInternet Protocol (IP) packets using mobile IP (MIP) addressing, theprocessing device comprising: interfaces for a plurality ofcommunication subsystems wirelessly communicating with external devicemobile units (MNs) in a corresponding plurality of networks; a memoryfor storing an AT IP address (ATA); and, a network address selector forsending an IP packet to a correspondent node (CN) using the ATA as thesource address, via a first MN with a first care-of-address (CoA). 12.The processing device of claim 11 wherein the network address selectorreceives an IP packet from the CN with the ATA listed as the destinationaddress, via the first MN.
 13. A multi-mode wireless communicationsaccess terminal (AT) with means for sending Internet Protocol (IP)packets using mobile IP (MIP) addressing, the AT comprising: means forwirelessly communicating with external device mobile units (MNs) in aplurality of networks; and, means for network selection, having an AT IPaddress (ATA) cross-referenced to a care-of-address (CoA) for each ofthe plurality of MNs, the network selection means selecting a firstnetwork for transmission and sending an IP packet to a correspondentnode (CN) using the ATA as the source address, via a first MN.
 14. TheAT of claim 13 wherein the network selection means receives an IP packetfrom the CN with the ATA listed as the destination address, via thefirst MN.
 15. In a multi-mode wireless communications access terminal(AT), a signal bearing medium tangibly embodying a program ofmachine-readable instructions executable by a digital processingapparatus to perform operations for mobile Internet Protocol (IP)addressing, the operations comprising: providing an AT having an IPaddress (ATA) and a care-of-address (CoA) in each of a plurality ofnetworks; from the plurality of networks, selecting a first network fortransmission; and, sending an IP packet to a correspondent node (CN) viaa first mobile node (MN) external device, using the ATA as a sourceaddress.